Talk by Giuliana Panieri at Centre for Ice and Climate

Tracking methane emissions with benthic foraminifera

Giuliana PanieriCentre of Excellence, Centre for Arctic Gas hydrate, Environment and climate - CAGEUiT The Arctic University of Norway

AbstractCoupling of methane emissions with global climate throughout the recent geological history of the Earth is established. However, the contribution of different methane sources in the global budget is still a matter of debate. Marine and terrestrial methane both contribute to atmospheric methane, but the intensity, duration, episodicity, and areal distribution of these emissions are poorly understood, particularly in the marine environment.

The Centre for Arctic Gas Hydrate, Environment and Climate (CAGE) is investigating the role of gas hydrates in arctic areas, and the effects that their dissociation will have on oceans and our global climate in the future. It is, therefore, critical to resolve the periodicity of methane seafloor emissions through time, in relation to past climate change with a special focus on periods of climate warming.

One of the problems in the investigation of methane emissions in the sedimentary record is the scarcity of well-defined proxies that can be used to establish the timing of such events. Benthic foraminifera are an important component of biomass in the present oceans. In addition to their interest as indicator species living in the largest habitat on Earth, their tests have been used in isotope and trace element analysis aimed at reconstructing past environments. Carbon isotope (13C) of foraminiferal tests affected by release of large volumes of isotopically light methane from the seafloor are much lower than those observed in non-seep environments. The hypothesis that benthic foraminifera could be used as proxies of local methane emissions from the seafloor has been verified by several studies.

Thus, in an effort to track changes of past methane emissions from the Arctic seafloor, we are conducting an intensive investigation in the Vestnesa Ridge (west of Svalbard at ~79° N), a large sediment drift in the Fram Strait representing one of the northernmost gas hydrate provinces along the Arctic continental margins. On-going results indicate that the geologic record in the area is punctuated by several methane emission events (MEEs) occurring at the site at least during the last 23,000 years.